Photographic colloid stratum transfer process



United States Patent 3,240,599 PHOTOGRAPH-EEC (IOLILOID STRATUM TRANSFER PRUQESS Edward C. Yaclrel and James G. rnith, both of Rochester,

N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed ept. 28, 1961, Ser. No. 141,297 13 tCiaims. (Cl. 96-28) This invention relates to photography and more particularly to a colloid stratum transfer process in photography.

In the processes of the Yutzy and Yackel US. Patents 2,596,756, May 13, 1952, 2,716,059, August 23, 1955, and related patents, unhardened gelatino silver halide emulsion layers are developed under conditions of tanning development and strata of the residual unhardened portions of the emulsion layers are caused to adhere to and transfer to a receiving sheet to provide a print thereon corresponding to a line or halftone subject. In these processes several prints are obtainable from a single exposed and developed emulsion layer by pressing the developed emulsion layer into contact with a succession of receiving sheets until the unhardened emulsion image areas are exhausted. In the process, during the transfer step, the strata of unhardened emulsion are physically detached from the emulsion layer with the result that the image obtained on the receiving sheet possesses an irregular contour and therefore has less definition than is desirable.

We have discovered that by use of a particular sensitive element in the process, a substantial improvement in definition of the image as well as substantial saving in time and materials is possible. In our process a sensitive element is used having a Water-resistant support, and coated thereon, an unhardened gelatino silver halide emulsion layer containing a gelatin tanning silver halide developing agent, the silver halide, gelatin and developing agent being present in a limited quantity and proportion such that only one high-quality print is obtained in the process and this print is obtained in substantially less time than previously thought to be possible.

The sensitive element of the invention includes a waterresistant support such as a polyethylene-coated paper support and upon the support is an emulsion layer containing from about 50 to 125 mg. of silver per square foot as silver halide, about 150 to 250 mg. of gelatin per square foot and about 50 to 100 mg. per square foot of a gelatin tanning silver halide developing agent (preferably a mixture of about 50 to 100 mg. of a gelatin tanning silver halide developing agent per square foot and less than about 50 mg. of a non-tanning silver halide developing agent per square foot). After the element has been exposed to a two-tone subject (a line or halftone subject), it can be activated with an alkaline solution preferably having a pH within a range of about 11 to 13 for about 2 to seconds, at moderately low temperatures of the order of 65 to 90 F., to develop the emulsion layer (compared to 15 to 30 seconds development for sensitive elements previously used in the processes). As a result of development, the less exposed and developed areas of the emulsion layer become very soft and the entire untanned areas, not just a stratum thereof, appear to fi-ow imagewise to the contiguous receiving sheet, with or Without application of heat, rather than partially adhering to the receiving sheet and being only partially torn away from the emulsion layer when the emulsion and sheet are separated as in the previous processes. In this process wherein a single high-quality print is obtained for which there is appreciable demand by the trade, the quantity of silver halide, gelatin and tanning silver halide developing agent in the emulsion is critical and is maintained within the mentioned proportions. Moreover, the support should be moisture resistant to insure that the emulsion initially coated thereon and the processing composition subsequently applied thereto will not unduly penetrate below the surface of the support during processing operattions and that the unhardened image areas will separate cleanly from the support in the transfer step. As a result, it is now possible to develop the emulsion for only about 2 to 10 seconds to attain the desired degree of development (rather than the previous 15 to 30 seconds) and this can best be accomplished if a strongly alkaline developer solution having a pH of about 11 to 13 is used. In variations of the process of the invention described below, the developing agent in the emulsion layer comprises one or more gelatin tanning silver halide developing agents or a mixture of a gelatin tanning silver halide developing agent and a non-tanning silver halide developing agent, depending on the particular requirements of the process. In some cases illustrated in the examples below, it is preferred that the alkaline solution used to initiate development merely be applied to the surface of the emulsion layer before placing the layer into contact with the receiving sheet. In this case it may be desirable to apply some heat at about -150 F. to complete development in minimum time of the order of 2 to 5 seconds. In this case alkaline developer solutions of lower pH can be used such as amine and organic hydroxide solutions. Thus, in apparatus wherein the emulsion is wetted with the alkaline solution and quickly brought into contact with the receiving sheet by passage over and between a series of rollers, one or more rollers may supply heat for the mentioned purpose. However, heat is not required in the process if the specified emulsion components including the mixture of tanning and non-tanning developing agents and strongly alkaline developing solution are used. In some cases the whole sensitive element may be immersed in the solution until development is complete after which the transfer operation is carried out. In either case, the whole unhardened image areas are transferred in substantially the same manner by merely pressing the developed element while moist into contact with the absorbent receiving surface to cause the unhardened emulsion regions to flow imagewise thereto and produce an image of high definition on the receiving surface.

The substantially unhardened gelatino silver halide emulsions used in the process should be no harder than specified in the patents mentioned above, i.e. not harder than a gelatin layer containing 0.7 gram of dry formaldehyde per pound of gelatin freshly coated, and ordinarily it is satisfactory to merely add the emulsion ingredients to an aqueous solution of ordinary gelatin without addition of any gelatin hardener.

The gelatin tanning silver halide developing agents used in the emulsion layers are those well known in the art, such as those dis-closed by US. Patent 2,716,059 above, eg hydroquinone, pyrocatechol and preferably the substantially non-diffusing gelatin tanning silver halide developing agents known in the art such as 3,4-dihydroxydiphenyl, 2,5-dihydroxydiphenyl, 2,3-dihydroxydiphenyl, etc.

The non-tanning silver halide developing agents useful in the process are also Well known in the art and are described in the above patent, e.g. p-phenylenediamine, paminophenol, p-rnethylaminophenol sulfate, 3-pyrazoliclones, e.g. l-phenyl-B-pyrazolidone, l-phenyl-4,4-dimethyl-3-pyrazolidone, etc. The self-coupling non-tanning silver halide developing agents, e.g. 4-methoxy-1-naphthol and S-hydroxy-l-naphthol are particularly useful in the sensitive elements in conjunction with the gelatin tanning silver halide developing agents. Ordinarily these gelatin tanning and non-tanning silver halide developing agents are employed in the emulsion layers; however, either or both may be present in the alkaline solution used'to initiate development of the emulsion layer.

The support for the emulsion layer should be waterresistant for reasons mentioned above and includes paper, film or other supports having a surface resistant to the penetration of moisture, for example, a water-resistant film support such as cellulose acetate, paper coated with or containing a water-resistant cellulose ester or synthetic polymer, such as cellulose acetate, polyethylene or polypropylene coated paper supports. Paper supports coated with or containing an a-olefin polymer are especially useful, the a-olefin preferably containing from about 2 to carbon atoms e.g. a-olefin homopolymers or copolymers such as polyethylene, polypropylene, ethylenepropylene copolymers, etc. Naturally, the water resistant surfaces of such supports should be suitably prepared to receive the unhardened emulsion layer by use of conventional subbing techniques. In the case of the u-olefin polymers such as polyethylene coated on paper supports, the surface thereof is conveniently electron bombarded with corona discharge to provide the desired contact angle of its surface as described in the Alsup and Venor US. patent application Serial No. 191,711 filed May 2, 1962, and in Modern Plastics, May 1961, pages l99206.

The alkaline solutions used to initiate and complete development of the exposed emulsion layers contains as an essential ingredient an organic or inorganic alkaline material, e.g. alkali metal carbonate and hydroxide, such that the solution is strongly alkaline and preferably has a pH within a range of about 11 to 13 so that development of the emulsion layer proceeds to completion in as short a time as possible. As mentioned, the prescribed combination of developing agent, silver halide and gelatin in the emulsion insures that development will be sufiiciently complete within about 2 to 10 seconds, that the unhardened image portions of the emulsion can be transferred to the receiving sheet to provide an image thereon having high definition.

The absorbent surface to which the colloid image transfer is made is not especially critical but should be reasonably hydrophilic and absorptive so as to receive the gelatin emulsion image flowing thereto from the exposed and processed emulsion layer. In the case of paper receiving sheets, it may be desirable to decrease its moisture absorption properities, for example, by application thereto of a solution of wax. Thus, a paper sheet was immersed in a solution of 0.1 gram of beeswax in 100 cc. of toluene, drained and dried. In this manner about 0.006 gram of wax per foot square was applied to the surface of the paper fibers and not as a uniform layer of wax on the paper. Thus, the paper fibers are coated with wax and the transferred image areas exhibit improved density and definition among other advantages.

The following examples will serve to illustrate our invention:

Example 1 An emulsion suitable for use in our process can be made by preparing solutions of (A) 100 grams of gelatin in 800 cc. of water at 40 C., (B) 100 grams of silver nitrate in 400 cc. of water at C. and (C) grams of sodium chloride in 400 cc. of water. Solutions B and C are simultaneously run into solution A at a uniform rate While stirring the latter over a period of about 10 minutes; solution B preferably not being allowed to run in faster than C. The pH of the emulsion may then be adjusted to 5.0. After washing, the emulsion was optically sensitized and the following additions were made to a portion of the emulsion containing one mole of silver halide.

500 grams of the following dispersion:

Solution 150 g. of a 10% aqueous gelatin solution, cc. of a 7.6% aqueous saponin solution, disperse at 40 C.

4 Solution 2100 g. of dibutyl phthalate, 50 g. 4-phenyl catechol, dissolve at 40 C.

Solution 2 was added to 1 and passed through a colloid mill. 15.0 mg. of Methylene Blue dye was added.

A coating aid was also added and the resultant emulsion was coated on a water resistant paper support at a coverage of 155 mg. silver/ft.

The coated paper was exposed to a line subject by reflex printing methods and passed through a processing machine, over a roller which applied an alkaline activator solution containing 5% dimethylamino ethanol to the surface of the emulsion, at a rate of one inch per second, and three seconds later the emulsion was brought into contact with a paper sheet and the sandwich passed between two rollers the one in contact with the receiving sheet being heated to a temperature of about to F. After passing through the rollers the sandwich was separated to obtain a high definition positive image of the subject upon the paper sheet composed of substantially all of the untanned image areas of the emulsion layer, not just a stratum thereof.

This example has illustrated a rapid colloid transfer process for yielding a copy wherein the activator solution is moderately alkaline and transfer is effected at elevated temperatures. However, the same sensitive element can be processed at room temperature using a longer transfer time and a more strongly alkaline activator solution such as potassium carbonate.

Example 2 This example illustrates a process particularly designed to operate at room temperature of the order of 68 F., i.e. utilizing strongly alkaline developing solution and a mixture of tanning and non-tanning developing agents, and producing prints in a relatively short time of the order of 5 seconds.

To one mole of the washed emulsion prepared in Example 1 was added 1.5 mg. Methylene Blue dye and 800 g. of the following dispersion:

Solution 1500 g. of a 10% aqueous gelatin solution, 50 cc. of a 7.6% aqueous saponion solution, disperse at 40 C.

Solution 2100 g. tri-o-cresyl phosphate, 20 g. 4-methoxy-l-naphthol, 30 g. 4-phenyl catechol, dissolve at 40 C.

Add Solution 2 to 1 and pass through a colloid mill. The resultant emulsion was coated upon an electron bombarded polyethylene coated paper support at a coverage of 200 mg. gelatin/ftF, 90 mg. silver/ft. and 75 mg. total developer/ftfi.

The coated paper was exposed to a line subject by reflex printing methods followed by development for 5 seconds with a 6.0% solution of potassium carbonate at room temperature. Thereafter, the emulsion was pressed into contact with a paper receiving sheet at room temperatures and at once the emulsion and receiving sheet were stripped apart to leave a high definition image on the sheet composed of substantially all of the less exposed areas of the emulsion layer, not just a stratum thereof, which had separated cleanly from the polyethylene surface.

In a similar manner other tanning and non-tanning developing agents may be used in the unhardened gelatino silver halide emulsions within the range specified to produce a single high definition transfer print.

What we claim is:

1. A light-sensitive substantially unhardened gelatinosilver halide emulsion layer on a polyethylene coated paper support, said emulsion layer containing per square foot about 50 to 125 mg. of silver as silver halide, about 50 to 100 mg. of a gelatin tanning silver halide developing agent, 0 to about 50 mg. of a gelatin non-tanning silver halide developing agent, and about to 250 mg. of gelatin, said emulsion being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated.

2. A light-sensitive substantially unhardened gelatinosilver halide emulsion layer on a polyethylene coated paper support, said emulsion layer containing per square foot about 50 to 125 mg. of silver as silver halide, about 50 to 100 mg. of a gelatin tanning silver halide developing agent selected from the class consisting of hydroquinone, pyrocatechol, 3,4 dihydroxydiphenyl, 2,5 dihydroxydiphenyl, and 2,3-dihydroxydiphenyl, 0 to about 50 mg. of a silver halide developingagent selected from the class consisting of p-aminophenol, p-phenylenediamine, pmethylaminophenol sulfate, 3-pyrazolidones, 8-hydroxyoc-naphthol and 4-methoxy-a-naphthol, and about 150 to 250 mg. of gelatin, said emulsion being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated.

3. A photographic colloid stratum process comprising developing an exposed emulsion layer on a polyethylene coated support, said emulsion layer comprising a substantially unhardened gelatino-silver halide emulsion containing per square foot about 50 to 125 mg. of silver as silver halide, about 50 to 100 mg. of a gelatin tanning silver halide developing agent, 0 to about 50 mg. of a gelatin non-tanning silver halide developing agent and about 150 to 250 mg. of gelatin, said emulsion layer being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, with an alkaline solution to obtain a hardened gelatin and silver image in the region of exposure to the highlight area and substantially unhardened gelatin, silver and silver halide in the region of the emulsion layer corresponding to the shadow region, pressing a sheet having an absorbent surface against said emulsion layer while said emulsion layer is moist to cause only the shadow region of the emulsion to adhere to said sheet, and separating said sheet and emulsion layer to transfer a stratum comprising substantially all of the unhardened gelatin of said shadow region of the emulsion layer to said sheet.

4. A photographic colloid stratum process comprising developing an exposed emulsion layer on a polyethylene coated support, said emulsion layer comprising a substantially unhardened gelatino-silver halide emulsion containing per square foot about 50 to 125 mg. of silver as silver halide, about 50 to 100 mg. of a gelatin tanning silver halide developing agent, 0 to about 50 mg. of a gelatin nontanning silver halide developing agent and about 150 to 250 mg. of gelatin, said emulsion layer being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, for about 2 to 10 seconds with an alkaline solution to obtain a hardened gelatin and silver image in the region of exposure to the highlight area and substantially unhardened gelatin, silver and silver halide in the region of the emulsion layer corresponding to the shadow region, pressing a sheet having an absorbent surface against said emulsion layer while said emulsion layer is moist to cause only the shadow region of the emulsion to adhere to said sheet, and separating said sheet and emulsion layer to transfer a stratum comprising substantially all of the unhardened gelatin of said shadow region of the emulsion layer to said sheet.

5. The process of claim 4 wherein the transfer of the unhardened emulsion regions is carried out at a temperature of about 100 to 150 F.

6. The process of claim 4 wherein the transfer of the unhardened emulsion regions is carried out at room temperature.

7. A light-sensitive substantially unhardened gelatinosilver halide emulsion layer on a water insoluble synthetic polymer coated paper support, said emulsion layer containing per square foot about 50 to 125 mg. of silver as silver halide, about 50 to 100 mg. of a gelatin tanning silver halide developing agent, 0 to about 50 mg. of a gelatin non-tanning silver halide developing agent, and about 150 to 250 mg. of gelatin, said emulsion being 6 not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated.

8. A light-sensitive substantially unhardened gelatinosilver halide emulsion layer on a water insoluble synthetic polymer coated paper support, said emulsion layer containing per square foot about 50 to 125 mg. of silver halide, about 50 to mg. of a gelatin tanning silver halide developing agent selected from the class consisting of hydroquinone, pyrocatechol, 3,4-dihydroxydiphenyl, 2,5-dihydroxydiphenyl, and 2,3-dihydroxydiphenyl, 0 to about 50 mg. of a gelatin non-tanning silver halide developing agent, and about 150 to 250 mg. of gelatin, said emulsion being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated.

9. A photographic colloid stratum process comprising developing an exposed emulsion layer on a water insoluble synthetic polymer coated paper support, said emulsion layer comprising a substantially unhardened gelatinosilver halide emulsion containing per square foot about 50 to mg. of silver as silver halide, about 50 to 100 mg. of a gelatin tanning silver halide developing agent, 0 to about 50 mg. of a gelatin non-tanning silver halide developing agent and about to 250 mg. of gelatin, said emulsion layer being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, with a strongly alkaline solution to obtain a hardened gelatin and silver image in the region of exposure to the highlight area and substantially unhardened gelatiin, silver and silver halide in the region of the emulsion layer corresponding to the shadow region, pressing a sheet having an absorbent surface against said emulsion layer while said emulsion layer is moist to cause only the shadow region of the emulsion to adhere to said sheet, and separating said sheet and emulsion layer to transfer a stratum comprising substantially all of the unhardened gelatin of said shadow region of the emulsion layer to said sheet.

10. A photographic colloid stratum process comprising developing an exposed emulsion layer on a water insoluble synthetic polymer coated paper support, said emulsion layer comprising a substantially unhardened gelatino-silver halide emulsion containing per square foot about 50125 mg. of silver as silver halide, about 50 to 100 mg. of a gelatin tanning silver halide developing agent, 0 to about 50 mg. of a gelatin non-tanning silver halide developing agent and about 150 to 250 mg. of gelatin, said emulsion layer being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, for about 2 to 10 seconds with an alkaline solution having a pH of 11 to- 13 to obtain a hardened gelatin and silver image in the region of exposure to the highlight area and substantially unhardened gelatin, silver and silver halide in the region of the emulsion layer corresponding to the shadow region, pressing a sheet having an absorbent surface against said emulsion layer While said emulsion layer is moist to cause only the shadow region of the emulsion to adhere to said sheet, and separating said sheet and emulsion layer to transfer a stratum comprising substantially all of the unhardened gelatin of said shadow region of the emulsion layer to said sheet.

11. The process of claim 10 wherein the transfer of the unhardened emulsion regions is carried out at a temperature of about 100 to 150 F.

12. The process of claim 10 wherein the transfer of the unhardened emulsion regions is carried out at room temperature.

13. A photographic colloid stratum process comprising developing an exposed emulsion layer on a water insoluble synthetic polymer coated paper support, said emulsion layer comprising a substantially unhardened gelatino-silver halide emulsion containing per square foot about 50 to 125 mg. of silver as silver halide, about 50 to 100 mg. of a gelatin tanning silver halide developing agent, 0 to about 50 mg. of a gelatin non-tanning silver halide developing agent and about 150 to 250 mg. of gelatin, said emulsion layer being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, with an alkaline solution having a pH of about 11-13 to obtain a hardened gelatin and silver image in the region of exposure to the highlight area and substantially unhardened gelatin, silver and silver halide in the region of the emulsion layer corresponding to the shadow region, pressing a sheet having an absorbent surface against said emulsion layer while said emulsion layer is moist to cause only the shadow region of the emulsion to adhere to said sheet, and separating said sheet and emulsion layer to transfer a stratum comprising substantially all of the unhardened gelatin of said shadow region of the emulsion layer to said sheet.

References Cited by the Examiner UNITED STATES PATENTS OTHER REFERENCES Hornsby: The British Journal of Photography, B. P. 655, 274, June 21, 1957, page 366.

15 NORMAN G. TORCHIN, Primary Examiner. 

1. A LIGHT-SENSITIVE SUBSTANTIALLY UNHARDENED GELATINOSILVER HALIDE EMULSION LAYER ON A POLYETHYLENE COATED PAPER SUPPORT, SAID EMULSION LAYER CONTAINING PER SQUARE FOOT ABOUT 50 TO 125 MG. OF SILVER AS SILVER HALIDE, ABOUT 50 TO 100 MG. OF A GELATIN TANNING SILVER HALIDE DEVELOPING AGENT, 0 TO ABOUT 50 MG. OF A GELATIN NON-TANNING SILVER HALIDE DEVELOPING AGENT, AND ABOUT 150 TO 250 MG. OF GELATIN, SAID EMULSION BEING NOT HARDER THAN A GELATIN LAYER CONTAINING 0.7 GRAM OF FORMALDEHYDE PER POUND OF GELATING FRESHLY COATED. 